Inflatable antenna structure



Nov. 17, 1959 WCUR Em 2,913,726

INFLATABLE ANTENNA STRUCTURE Filed Oct. 29, 1956 WITNESSES J JvNVcENT ORsa A omes urne W HBu gan L. Jackson.

- ATTORNEY INFLATABLE ANTENNA STRUCTURE James W. Currie, Baltimore, and Hagan L. Jackson, Catonsville, Md., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 29, 1956, Serial No. 619,050

8 Claims. (Cl. 343872) This invention relates to a lightweight antenna assembly, and more particularly to an inflatable antenna structure which may be deflated and packed in shipping containers of small volume. The invention has particular, but by no means exclusive, utility as a radar antenna which may be easily and rapidly assembled or dismantled and transported for military purposes.

It is a primary object of this invention to provide an inflatable lightweight antenna structure. As will become apparent from the following description, the antenna of the present invention comprises a pair of paraboloids joined at their rims to form an inflatable housing which is supported in an upright position on a rotatable base. One of the paraboloids has its inner surface coated with wave energy reflective material so that when the housing is inflated, the coated paraboloid assumes the configuration of a parabolic antenna reflector.

Another object of the invention is to provide an antenna assembly incorporating an air-supported radome to protect the antenna, associated electronic equipment, and operating personnel from high winds and ice loads.

The above and other objects and features of the invention will become apparent from the following detailed description taken in connection with the accompanying single figure drawing which is a broken away view of the antenna of the invention.

Referring to the drawing, there is shown an inflatable antenna structure 10 which is formed from a combina tion of fabrics such as vinyl-coated fiberglass, neoprenecoated nylon, and lightweight rigid support members. The antenna is assembled from two paraboloids of revolution 12 and 14 joined together at their rims and inflated to approximately 0.02 p.s.i. above the surrounding pressure. When inflated, the two paraboloids are stabilized by a generally annular tube 16 which is incorporated into the rim of the antenna and inflated to approximately 10 p.s.i. Each of the paraboloids of revolution 12 and 14 is formed from a plurality of substantially triangular fabric sections and is fastened at its periphery to the tube 16 by any suitable means, such as a zipper.

The fabric paraboloids are cut off at the bottom to provide a suitable area for attachment to a folding structural base 18 of lightweight metal. The tube 16 is attached to base 18 at its two extremities by light castings to form a stiff and stable arch which is the main structural member of the balloon. The entire base 18 is supported on a shaft 20 which is carried for rotation on a tripod assembly 22 at a height sufficient to provide work space for operating personnel below the antenna, where the radar electronic equipment is located. Means, not shown, are provided to drive shaft 20 and impart scanning motions to the antenna.

The antenna reflector itself 24 is formed from a sheet of Mylar plastic that has been coated with aluminum or other suitable wave energy reflective material. The reflecting surface is attached to the inner surface of one of the paraboloids 12, substantially as shown. Since the other fiberglass paraboloid 14 is not coated with wave energy reflective material, it will be transparent to all radio frequency energy and the field of the reflector will be essentially unobstructed. A wave energy feed horn 26 is employed to convey radio frequency energy between the reflector 24 and the radar electronic equipment, not shown, in a manner too well known to warrant further description here.

The radome 28 for the inflatable antenna 10 and its associated electronic equipment comprises a spherical structure of neoprene-coated nylon or other suitable fabric mounted directly on the ground. Like the antenna, the radome may be made in sections which are fastened together before inflation. When the radome is inflated, the air pressure within the assembly, approximately 0.17 p.s.i. above atmospheric, does not cause discomfort to operating personnel. The radome is stabilized by a suitable number of guy wires 30 which are anchored to the ground. Entrance to the radome is through an air lock 32.

Blowers 34 and 36 of sufiicient capacity and suitably flat pressure volume characteristics are used for both the antenna structure 10 and the radome 28. A compressor 37 inflates the annular tube 16. Air pressure inside the antenna is maintained greater than air pressure within the radome by a fixed amount to maintain the close tolerances needed on the surface of the reflector 24 and to prevent any distortion of the radar transmission and reception pattern. Large variations in the amount of air leakage from either inflated area will not result in large pressure changes because of the essentially flat pressure-volume characteristics of the blowers. This, coupled with rip-resistant fabric, makes the complete system insensitive to minor tears caused by wind-blown objects or projectiles.

The assembly of the complete system can be quickly accomplished with no special erection fixtures. Only rough leveling of the ground area is necessary. A base circle for the radome is first laid out and the ground anchors are driven. Then a ground cloth is spread over the ground surface and the antenna structure and electronic equipment placed on it. The radome side sections are anchored to the ground anchors and fastened to each other by zippers. Thereafter, the blowers for the radome are started and the radome is inflated. A block and tackle is attached to the center of the radome crown piece and used to assemble the tripod 22, the antenna base 18 which is erected on top of the tripod, and the air-inflated tube 16 and paraboloids 12 and 14 which are zippered to the base and to each other. Blower 36 and compressor 37 then inflate the antenna and tube 16. During inflation the electronic cables are connected and the electronic equipment set in place.

It can thus be seen that the present invention provides an extremely lightweight antenna which may be easily transported and assembled in a matter of minutes.

Although the invention has been shown in connection with a certain specific embodiment, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope of the invention.

We claim as our invention:

1. In an antenna system, an inflated housing of nonconductive material having a portal for entrance and exit of operating personnel, and an inflatable antenna reflector structure disposed within and rotatable relative to said housing.

2. In an antenna system, an inflated housing of nonconductive material having a portal for entrance and exit of operating personnel, a base member positioned 'and rotatable relative to said housing, an inflatable balloon structure generaly' spheroidal in shape carried by said base member and disposed within said housing to provide Workspace therebelow for operating personnel,

wave energy reflective material carried on a wall of said'balloon structure, and means positioned within'the balloon structure for directing wave energy against said wave energy reflective material.

4. In an antenna'system, an inflated housing for equip mentand personnel, an inflated balloon structure disposedwithin and rotatable relative to said housing, wave energy reflective material arranged on a wall of said balloon structure to assume the shape of a generally parabolic antenna, and 'a feed mechanism within the balloon structure to direct wave energy toward the Wave energy reflective material.

5. In an antenna system, an inflatable housing for equipment and personnel, means for maintaining the pressure within said housing above atmospheric pressure, an inflatable balloon structure disposed within and rotatable relative to'said housing, means for maintaining the pressure within the balloon structure above the pressure existing in said housing, wave energy reflective material arranged on a wall of said balloon structure to assume the shape of a general-1y parabolic antenna reflector, and a wave energy feed mechanism for said reflector.

6. In an antenna system, an inflatable housing for equipment and personnel, a base member disposed within and rotatable relative to said housing, an inflatable balloon structure fastened to said base member, wave energy reflective material arranged within said balloon structure to assume the shape of a generally parabolic antenna reflector, and means for maintaining a pressure differential between the interior of said housing and the interior of said balloon structure.

7. In an antenna system, an inflated housing of flexible non-conductive material and of generally spherical shape for equipment and personnel, a base member positioned Within and rotatable relative to said housing, a balloon structure carried by said base member and comprising a pair of dish-shaped spheroidal sections of inflatable material joined at their peripheries, wave energy reflective material positioned on a surface of one of the spheroidal sections to form an antenna reflector, and means for feeding wave energy to said reflector.

8. In an antenna system, an inflated housing of flexible non-conducting material for equipment and personnel, a base member positioned Within and rotatable relative to said housing, a generally annular inflated tube carried by said rotatable base member, a pair of dish shaped sections of flexible material joined at their pe ripheries to said tube to form an inflatable balloon structure in which the dish-shaped sections assume a generally parabolic configuration when the balloon structure is inflated, Wave energy reflective material fixed to a surface of one of said dish-shaped sections to form a directive antenna configuration when the balloon structure is inflated, and means positioned Within said balloon struc ture for feeding wave energy to said antenna configuration References Cited in the file of this patent UNITED STATES PATENTS 2,463,517 Chromak Mar. 8, 1949 2,560,218 Dunlap July 10, 1951 2,780,806 Van Alstyne Feb. 5, 1957 2,814,038 Miller Nov. 19, 1957 

